Tuesday, August 25, 2009

Michael C. Feathers: Seven Blind Alleys in Software Design

sackgasse3_web.jpg Michael Feathers (author of Working Effectively with Legacy Code) gave an interesting talk at the Norwegian Developer Conference:
Seven Blind Alleys in Software Design.

The video of the talk can be found on this page.

Here is a short transcript of the seven dead alleys he identified:

1. Programming in Pictures
  • This has been a pipe-dream for years and years in the software industry.
  • "Anybody remember MDA?" (note the notion of the past ;-)
  • Some complexity is irreducible.
  • Pictures are not necessary better than words!
  • Word language symbolism vs. letter language symbolism. Thats the options we have, regardless if visual or textual.
  • Where are the real systems?
  • Think about the edge-cases.

  • 2. Metaprogramming
  • A result from the notion that it is hard to change code.
  • The promise is that it is easier to change data that represents things in the code.
  • We have to remember that code is data anyway.
  • Flexiblity vs. Understandability
  • Complexity is not reduced with flexibility.
  • Its hard to figure out what's going on in production.

  • 3. The Ultimate Abstraction
  • It always just seems one step away.
  • Believing in perfection
  • People don't want to make compromises
  • Programmers are abstraction junkies
  • Striving for the grand unified theory
  • Indicator: attempt to unify one and many
  • Deadlines and budgets help

  • 4. The perfect taxonomy
  • Do not try to create it upfront. Let it evolve and hope that it eventually will become stable.
  • Do not generalize too early -> failed framework projects.
  • Abstractions just have to be good enough not perfect.
  • English is ambiguous, programming ought not to be.

  • 5. Modeling the real world
  • Software is really different, it is subject to tighter constraints than the real word
  • If we can borrow concepts from the domain for our code, then that is great, but we don't have to.
  • Behavior is key. We can't always find a metaphor. We don't have to be limited by the concepts in the domain. We can make stuff up.
  • Why would you want to model the real world, thats where the problems are!
  • Classical example: Liskov substitution princple (Square/Rectangle)

  • 6. Code generation
  • Accept: You are never going to be complete! Don't be ambitious!
  • Traps! Can be shaping the code in bad ways.
  • Effect: De-skilling development
  • Encodes advanced knowledge of the domain which is likely to be wrong - workarounds are inevitable and get even the norm the older the system gets
  • Cruft buckets - Places where developers are forced to put their code. No design freedom possibe! Complexity cannot be tackled!

  • 7. Natural Languages
  • Business people are never going to be able to program - even in plain english
  • Programming is always going to be more constrained than plain english is
  • English seems easier, it does read better, but you have to think like a programmer!

  • I can't say that I always agree, but this presentation really allows you to take a step back and reflect. Michael addresses a lot of current and reoccurring hypes, and lets us remeber that there is no silver bullet.


    1. Highly interesting.
      Like you, I am not sure I agree with everything, but I agree with most of the points.

      Michael did an excellent job in mapping the false hopes of our industry.

    2. "Comlexity cannot be tackled!"



    3. Sharp observations. I think that a lot of these alleys aren't absolutely blind (i.e. useless) but are often myopic (misleading the software writer into ignoring the trade-offs of his/her favorite "alley" and producing unmanageable code).

    4. @Art
      "Myopic" - Interesting analogy! Thanks!

    5. Funny that after all these years, we never managed to reduce complexity. Attempts to bridge the real-world with software concepts are hindered by the law of 1, 0 and nothing in-between. Fuzzy computers to the rescue, maybe?

    6. One line of code is worth a thousand flowcharts.....

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    8. These are brilliant points! You are very clever coming up with this list.


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